Archive for the ‘Pests’ Category

Decades-old DNA match aids battle against pasture pests

AgResearch research associate Nicky Richards and her colleagues, recently confronted with a Porina (Wiseana) caterpillar found in Southland, were challenged with identifying which species of the pasture-munching Porina pest they were looking at.

Some species of Porina pose a much greater threat to pasture on New Zealand farms than others. Although seven Porina species are recognised, and the species can be identified by sight at the adult moth stage, it is impossible to do the same with the caterpillars because they look identical.

The research team suspected the caterpillar found in Southland was from an elusive Porina species known as Wiseana (W.) fuliginea.

To confirm this they needed to analyse an adult moth of the same species.

Mrs Richards explains:

“Unfortunately, no adult W. fuliginea had been found by us in our previous 20 years of field collections. So we had to find another way. Our connections led us to museum specimens held in the New Zealand Arthropod Collection hosted by Landcare Research. There we found dried adult W. fuligineaspecimens that had been identified and preserved after their deaths 33 years ago.”

“We took legs from these long-dead moths to generate genetic sequences – which takes more work when the DNA has broken down over time. It’s basically like putting together pieces of overlapping Lego to build what you need.”

Information gleaned from the 33-year-old specimens proved identical to the sequence from the caterpillar found in Southland. In other words, the researchers had a DNA match.

The work has helped in the development of a new DNA-based method to identify Porina caterpillars. By building a better understanding of this pest, scientists can learn how best to help farmers prevent the hundreds of millions of dollars of damage it can do to pasture on New Zealand’s farms each year.

Environmentally friendly treatments for Porina outbreaks can be explored and species that are the key pasture annihilators targeted, Richards said.

More can be learned about Porina and other pests at


Good news for bees? Varroa mites have genetic holes in their armour

Seemingly indestructible Varroa mites have decimated honeybee populations and are a primary cause of colony collapse disorder, or CCD.

Zachary Huang, an entomologist at Michigan State University, describes the mite is the greatest threat to honeybee health worldwide,

“They have developed resistance to many pesticides, so it’s urgent that we explore and target these genes to develop better control methods.”

A promising development is the discovery by MSU scientists of genetic holes in the pests’ armour that could potentially reduce or eliminate the marauding invaders.

The team’s results, published in the current issue of Insect Science, have identified four genes critical for survival and two that directly affect reproduction.

The mite sucks the blood of honeybees and transmits deadly viruses. Its lifecycle consists of two phases: one where they feed on adult bees (the phoretic phase) and a reproductive phase that takes place within a sealed honeycomb cell, where the mites lay eggs on a developing bee larva.

The double-whammy of eating bees and spreading disease makes Varroa mites the number-one suspect of honeybee population declines worldwide.

Controlling such pests depends on either eliminating them or reducing their ability to reproduce. The MSU team used RNA interference to identify the key genes, which could achieve these outcomes. They injected the mites with double-stranded RNA, or dsRNA.

Interfering reduces transcription of a specific gene, the first step of making a gene, a piece of DNA, into a protein. This process, also known as “gene knockdown,” has been successful in reducing the mating success and the number of eggs produced by cattle ticks, which threaten cows and other livestock around the world.

Using this approach, the team identified two genes that caused high mortality in Varroa mites — Da and Pros26S. In fact, Da killed more than 96 percent of mites. They also identified four genes — RpL8, RpL11, RpP0 and RpS13 — that control reproduction.

Earlier research has shown that a combination of dsRNAs can be fed to bees at the colony level. Varroa mites absorb the “genetic cocktail” via bee blood and their population was reduced. Future research will explore whether a single-gene approach can be scaled up and achieve the same effect at a colony-wide setting. Using a single gene with a known mechanism will be more cost effective and safe to the honeybees.

The results may have applications beyond honeybees, too.

“It’s worth noting that Da reduced reproduction in species of mosquitoes and Drosophila,” Huang said.

Future research could help not only protect honeybees, but also reduce disease-carrying mosquitoes or crop-damaging pests, he said.

Huge savings estimated from wasp introduced to curb clover root weevil

A humble Irish wasp has saved New Zealand almost half a billion dollars, AgResearch estimates.

The estimates also show that the benefits of the introduction of the wasp by AgResearch to control the highly destructive clover root weevil are expected to continue at an ongoing rate of at least $158 million a year.

The total benefit of the biological control programme from 2006 – when the imported wasp was first released in an experimental phase – through to this year is estimated at at least $489m. This is based on reduced production losses on sheep and beef farms, and reduced use of urea fertiliser to compensate for damage from the weevil.

“It’s a fantastic example of how our science is making a real and profound difference to our agricultural sector and economy,” says AgResearch Science Team Leader Alison Popay.

“It’s also a real success story in the continuing battle against pests on New Zealand’s farms.”

The clover root weevil, an invasive pest from the northern hemisphere which feeds on clover, was first detected in New Zealand in 1996. A 2005 study estimated that without control it could cut farm margins by 10 to 15 per cent.

AgResearch started a research and development programme in 1996, and after testing to ensure its safety, the Irish wasp was cleared for release in New Zealand in 2005. It spread around the country with releases by AgResearch, and as wasps were provided to farmers.

The programme research and development costs have been about $8.2 million.

The wasp injects its eggs in the adult root weevil, and the resulting grubs inside the weevil render it infertile. Once fully grown, the grub kills the weevil as it eats its way out. One wasp can kill about 85 clover root weevils.

“The wasp was so successful the team found that it reduced weevil populations by around 90 per cent in monitored areas where the wasp is well established,” Dr Popay says.

The control programme has been supported by DairyNZ, Beef + Lamb New Zealand, Federated Farmers, the Clover Root Weevil Action group, the New Zealand Landcare Trust and fertiliser companies.


Govt musters resources for campaign to rid NZ of predators by 2050

The Government has announced plans to set up a new public-private partnership company by the beginning of 2017 to help fund regional large-scale predator eradication programmes.

Its aim is to achieving the goal of a Predator Free New Zealand by 2050.

This will require a massive team effort across the public, private, iwi and community sectors, Conservation Minister Maggie Barry says.

The Predator Free 2050 Project will combine the resources of lead government agencies the Department of Conservation and the Ministry for Primary Industries to work in partnership with local communities.

Under the strategy a new government company, Predator Free New Zealand Limited, will sponsor community partnerships and pest eradication efforts around the country.

Not all the technology to make New Zealand predator free yet exists, and the Biological Heritage National Science Challenge will have an important role in developing the science to achieve the predator free goal.

“By bringing together central and local government, iwi, philanthropists, and community groups, we know that we can tackle large-scale predator free projects in regions around New Zealand,” Ms Barry says.

“Project Taranaki Mounga and Cape to City in Hawke’s Bay are great examples of what’s possible when people join forces to work towards a goal not achievable by any individual alone.”

Primary Industries Minister Nathan Guy says the goal of a Predator Free New Zealand by 2050 will have major positive impacts for farmers and the wider primary sector.

“Possums and ferrets are the main carriers of bovine TB, which is a very destructive disease for cattle and deer. In this year’s Budget the Government committed $100 million towards combined eradication efforts with industry starting with cattle and deer by 2026,” Mr Guy says.

“By pooling our resources and working together we can jointly achieve our goals of both eradicating bovine TB, and achieving a predator free New Zealand.”

Science and Innovation Minister Steven Joyce says the Biological Heritage Challenge has an established network of scientists who are ready and willing to take on the Predator Free Challenge.

“For the first time technology is starting to make feasible what previously seemed like an unattainable dream.”

Predator Free New Zealand Limited will have a board of directors made up of government, private sector, and scientific players. The board’s job will be to work on each regional project with iwi and community conservation groups and attract $2 of private sector and local government funding for every $1 of government funding.

Four goals for 2025 have been set for the project:

  • An additional 1 million hectares of land where pests have been supressed or removed through Predator Free New Zealand partnerships;
  • Development of a scientific breakthrough capable of removing at least one small mammalian predator from New Zealand entirely;
  • Demonstrate areas of more than 20,000 hectares can be predator free without the use of fences;
  • Complete removal of all introduced predators from offshore island nature reserves

Ms Barry says these are ambitious targets in themselves, “but ones that we are capable of reaching if we work together”.

Approval is sought to introduce new virus to control rabbits

A new strain of virus, called RHDV1-K5, is reported to have the potential to help New Zealand farmers slash rabbit numbers by up to 30 per cent.

The virus is a Korean strain of the lethal calicivirus already present in New Zealand that causes rabbit haemorrhagic disease (RHD).

The New Zealand Rabbit Coordination Group is working with Landcare Research to seek approval to introduce K5 into New Zealand to help control rabbit damage which costs the agricultural industry tens of millions in control and lost production each year.

Dr Janine Duckworth, leader of Landcare Research’s rabbit biocontrol initiative, hopes the virus will be approved for release in New Zealand next autumn. Approval from the Ministry for Primary Industries and the Environment Protection Authority is required before it can be imported.

Duckworth said K5 had undergone thorough testing in Australia, where it is likely to be approved for release later this year.

“They’ve been testing lots of different strains and K5 is the one that looks the best. It could reduce rabbit numbers between 25 and 30 per cent,” Duckworth said.

K5 isn’t a “silver bullet” to New Zealand’s rabbit problem, she cautioned.

“It’s hard to imagine there will ever be a silver bullet to eradicate rabbits,” she said.

But the new strain of virus will provide farmers with a more cost-effective and efficient solution than strains currently in the field today. This should make follow-up with conventional trapping, shooting and dogs more effective and worthwhile too, Duckworth said.

The first strain of RHD, which was illegally imported in 1997, had a “huge impact” but an increasing proportion of rabbits have become immune to the disease.

While K5 is expected to make a dent in rabbit numbers, Duckworth did not believe it would make as big an impact as RHD did when it was first introduced. The K5 strain will be a boost to rabbit control by killing some of the immune rabbits.

Because rabbit numbers have surged this year due to the good summer and mild winter, Duckworth was worried some farmers may take matters into their own hands and try to illegally import the virus in from Australia.

“We don’t want an illegal release of the K5 strain. We want to ensure that control agencies use a commercially-prepared product, free from any unwanted viruses and that the timing and method of release is managed to ensure the best possible rabbit control outcomes for farmers.”

A vaccine is available for owners of domestic rabbits to protect their pets from the virus.

Submissions sought on agent to combat tomato, potato, capsicum and tamarillo pest

The Environmental Protection Authority  has opened submissions on an application to release a type of parasitic wasp as a biological control agent to combat a psyllid (plant louse) that attacks tomatoes, potatoes, capsicums and tamarillos in New Zealand.

The application, from Horticulture New Zealand Inc, on behalf of a number of growers’ industry groups, seeks approval to release the psyllid parasitoid Tamarixia triozae (the wasp) to kill the tomato potato psyllid or TPP (Bactericera cockerelli). This application was made under the Hazardous Substances and New Organisms (HSNO) Act 1996.

“Biological control is where the natural enemies of a plant pest (weed) or insect pest are released to reduce, eradicate and / or control those pests. We’re notifying this application to ensure that the EPA can consider all views about potential risks and benefits of introducing Tamarixia triozae into New Zealand,” said Applications and Assessment General Manager Sarah Gardner.

The psyllid was first found in New Zealand in 2006. It has been reported as a pest in several countries. If left without control it can have a significant impact on plant health and crop yield.

The psyllid has three life stages – egg, nymph and adult. Adult females lay eggs on the upper and lower surface of potato, tomato, capsicum and tamarillo plant leaves. Both nymphs and adults feed on the underside of leaves, causing discoloration and stunting of the plant, with poor or little fruit growth.

The psyllid is also known to transmit a bacterial pathogen that causes Zebra Chip disease in some horticulture crops, like potatoes, which also impacts crop yields.
Tamarixia triozae is a parasitoid which means it attaches to or within a single host and eventually kills it. It is a small, black, winged red-eyed wasp that is found mainly in North America and Mexico. It lays its eggs on the surface of psyllid nymphs (the host). Once hatched, the eggs develop into larvae that feed on the psyllid nymphs, eventually killing them

If released as a biological control, Tamarixia triozae will establish self-sustaining populations, meaning it will be able to live and reproduce without any human intervention in the New Zealand environment. The application concludes that this would reduce psyllid pressures on potatoes, tomatoes and other solanaceous crops. If released Tamarixia triozae will not be constrained in the environment and its movement and interaction with other species will be unrestricted.

The applicant notes that Tamarixia triozae would be part of an integrated pest management programme, using the natural enemies of psyllid to achieve effective control in combination with traditional and chemical control strategies.

Application details can be viewed here.

The submission period closes at 5pm on 24 March.

Rigorous tests for potential wasp biocontrol

Tests will soon begin to ensure a mite, with the potential to be used as a biocontrol agent against wasps, isn’t a threat to bees.

The mite, discovered by Landcare Research scientist Dr Bob Brown on wasp nests in 2012, recently has been recognised as a new species and named Pneumolaelaps niutirani.

It was identified and named by fellow Landcare Research scientist Dr Zhi-Qiang Zhang and Ministry for Primary Industries scientist Dr Qing-Hai Fan.

Dr Brown has been researching the mites’ potential as a biocontrol agent against wasps, which cost the country’s primary industries around $130 million a year and cause biodiversity loses.

He has found wasp nests where the mites are present are 50 to 70 per cent smaller than uninfested nests. Immature mites have also been found in nests indicating wasps could be a host.

However, other species in the genus of the mites are often found in association with bees. As a result, the next step is to conduct safety trials to make sure the mite does not pose a risk to honeybees or bumblebees.

In order to do this, bee larvae would be fed stable isotopes and the mites later inspected to see if it was in their system, Dr Brown said.

“Stable isotopes are molecules that act like a chemical marker that we can track. If the stable isotopes are found in the mites this will conclusively tell us they are feeding on the bees because there is no other way for them to acquire these molecules,” he said.

“We found the mites in low numbers in quite a few honeybee hives so we need to check out what their association is. It’s not uncommon for organisms to have a different association with other species and feed on different things. It is possible the mites are there because they hitched a ride on wasps that were robbing honey from the hive.”

The tests would begin as soon as Dr Brown had excavated wasp nests over the coming months and had access to the mites. Once complete, attention would turn to checking the mites were not harmful to native bees.

Dr Brown will also investigate the associations between the mites and wasps. In particular, if and how the mites are responsible for decreased aggression levels in the wasps and how they are managing to enter the nests.

“Wasps don’t like anything in their nest but somehow these mites are tricking them into letting them be there.”

He wanted to thank the public for their support after an appeal for wasp queens to assist his research saw him sent 436 from around the country. An analysis of the wasps found 35 per cent had a least one mite.

The Vespula Biocontrol Action Group contracted Landcare Research to investigate the mite’s potential as a biocontrol agent against wasps.

The research is funded by the Ministry of Primary Industries’ Sustainable Farming Fund.